Three of the most widely used tumour profiling tests are the Oncotype DX Recurrence Score (RS) [3], Prosigna risk of recurrence (ROR) score often known as the PAM50 [4] and EndoPredict (EP/EPclin) [5], which provide an estimate of the 10-year risk of distant recurrence assuming 5 years of adjuvant endocrine therapy without chemotherapy and are endorsed for use in ER-positive, human epidermal growth factor receptor-2 (HER2)-negative and lymph node-negative disease in authoritative guidelines [6, 7]. The gene discussed is ESR1; the disease is neoplasm.